apply pep-612 to hybrid_method; accept SQLCoreOperations

apply pep-612 to hybrid_method; accept SQLCoreOperations

Fixes to the annotations within the ``sqlalchemy.ext.hybrid`` extension for
more effective typing of user-defined methods. The typing now uses
:pep:`612` features, now supported by recent versions of Mypy, to maintain
argument signatures for :class:`.hybrid_method`. Return values for hybrid
methods are accepted as SQL expressions in contexts such as
:meth:`_sql.Select.where` while still supporting SQL methods.

Fixes: #9096
Change-Id: Id4e3a38ec50e415220dfc5f022281b11bb262469